Pre-Lithiated Cathodes for Irreversible Lithium Loss Compensation
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Solution Overview
Problem
Lithium-ion cells face limitations in energy density due to irreversible capacity losses during initial charge or cycling, primarily attributed to surface passivation and coulombic inefficiency, especially with high-capacity alloy anodes like Si, Ge, and Sn, which lead to reduced cyclable capacity and energy density.
Innovation Solution
Pre-lithiation of cathode materials by chemically or electrochemically depositing lithium into cathode active materials before assembly into the cell, using processes like reel-to-reel web processing or electrochemical cells with controlled current and voltage, to supply extra lithium and enhance energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-capacity alloy anode materials (Si, Ge, Sn) are used to increase energy density, then the cell's energy density increases, but irreversible lithium consumption increases due to large volume changes and surface passivation
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the cathode material before cell assembly. This involves treating the cathode with lithium in advance (through chemical or electrochemical methods) so that when the cell operates, the pre-added lithium compensates for the irreversible consumption at the anode, thereby maintaining higher cyclable capacity and energy density throughout cycling.
2Quantity of substance
If lithium is added to compensate for anode irreversible consumption, then cyclable capacity increases, but cell assembly complexity increases
Solution Approach 1:
The patent merges the lithium compensation function into the cathode material itself rather than adding separate lithium sources. By incorporating lithium directly into the cathode structure (forming pre-lithiated cathode materials), the invention combines the energy storage function with the lithium compensation function in a single component, simplifying cell assembly while maintaining high cyclable capacity.
3Use of energy by moving object
If pre-lithiation is performed to increase initial charge capacity, then energy density improves, but manufacturing process complexity increases
Solution Approach 1:
The patent replaces mechanical/physical lithium addition methods with electrochemical or chemical pre-lithiation processes. Instead of mechanically mixing lithium powder with cathode materials, the invention uses electrochemical reduction (applying voltage) or chemical reactions to deposit lithium onto the cathode, providing more controlled and uniform pre-lithiation while simplifying subsequent manufacturing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The pre-lithiation process increases the initial charge capacity of cathodes, improves cycling efficiency, and stabilizes the cathode, leading to higher energy density and longer cycle life without compromising the anode's performance, thus overcoming the limitations of traditional lithiation methods.
Implementation Method 1
When the cell is charged for the first time, all the lithium that can be reversibly extracted from the cathode (or positive electrode) by electrochemical oxidation is transferred to the anode (or the negative electrode).
Implementation Method 2
all the lithium that can be reversibly extracted from the cathode (or positive electrode) by electrochemical oxidation is transferred to the anode
Implementation Method 3
Irreversible electrolyte reduction processes consume both charge and active lithium to form passivating films on the anode surface, known as solid electrolyte interphase (SEI), that prevent further reduction of the electrolyte.
Data Source
AI summary
Provided are methods of making and using pre-lithiated cathodes for use in lithium ion secondary cells as the means of supplying extra lithium to the cell. The chemically or electrochemically pre-lithiated cathodes include cathode active material that is pre-lithiated prior to assembly into an electrochemical cell. The process of producing pre-lithiated cathodes includes contacting a cathode active material to an electrolyte, the electrolyte further contacting a counter electrode lithium source and applying an electric potential or current to the cathode active material and the lithium source thereby pre-lithiating the cathode active material with lithium.